Reactions of Chiral Molecules

Reactions of Chiral Molecules involve changes where chirality may be retained, inverted, or lost, influencing drug activity and biological effects.

• Reactions involving chiral molecules are influenced by stereochemistry, leading to different outcomes based on the chirality.

1. Racemization

   • A reaction where a single enantiomer is converted into an equal mixture of both enantiomers (racemic mixture).
   • Racemic mixtures are optically inactive because the effects of the two enantiomers cancel each other out.
   • Example:
     • Heating lactic acid may cause racemization.

2. Resolution

   • Separation of a racemic mixture into its individual enantiomers.
   • Usually done using:
   • Chiral resolving agents
   • Crystallization
   • Chromatography

3. Reactions with Chiral Reagents

   • When a chiral reagent reacts with a chiral molecule, diastereomeric products may be formed.
   • Diastereomers have different properties and can be separated.

4. Stereoselective Reactions

   • Reactions where one stereoisomer is formed preferentially over the other.
   • Can be:
     • Enantioselective: One enantiomer is preferred
     • Diastereoselective: One diastereomer is preferred
   • Example:
     • Hydrogenation of chiral alkenes using chiral catalysts.

5. Inversion of Configuration (SN2 Reactions)

   • In SN2 nucleophilic substitution, the nucleophile attacks from the backside, causing an inversion of configuration at the chiral center.
   • Example:
     • Reaction of (R)-2-bromobutane with OH⁻ gives (S)-2-butanol.

6. Retention of Configuration

   • Some reactions maintain the configuration (no inversion).
   • Often observed in SN1 reactions, although racemization is more common due to the planar intermediate.

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